Nowadays, optical elements such as lenses are commonly used in digital cameras or digital video recorders. There is more and more demand for higher quality and serviceability of these optical elements. A film such as an anti reflective film or an infra-red cut film is generally applied onto the optical elements, especially on lenses. To improve imaging quality, it is an important first step to wash the optical elements before applying a film thereon. How to wash optical elements effectively before plating is therefore an important area of development.
Generally, optical elements are washed using ultrasonic waves in a vessel filled with liquid. However, the optical elements are prone to collide with each other during washing by the ultrasonic waves. As a result, a surface of each optical element can easily become scraped or damaged. Therefore, optical elements need to be fixed in a clamping apparatus so that the optical elements are separated from each other and do not collide with each other.
Referring to FIG. 8, a typical clamping apparatus is a holding board 40 defining a plurality of receiving holes 41. Each of the receiving holes 41 has a shape and size corresponding to one of optical elements (not shown). In use, each of the optical elements is received in one of the receiving holes 41, and the holding board 40 is then put in a liquid to be cleaned by concussion of ultrasonic waves. Because all the optical elements are received in the receiving holes 41, impurities on surfaces of the optical elements touching the holding board 4 are not easy to clean, thus, the washing effect is not good.
Therefore, a new clamping apparatus for clamping optical elements is desired in order to overcome the above-described shortcomings.